There is still a sense of novelty and high drama when an air ambulance swoops down on the scene of a road crash or some other serious accident. But rescue helicopters have become part of the fabric of the emergency services over the past 25 years, with one taking off somewhere in Britain every 10 minutes during daylight hours, and they have done so without most of us knowing very much at all about how they operate or who pays for them.

The truth is that air ambulances have been set up across the country with no overall planning, no agreed funding and no clear, bespoke system of regulation. As a result, there is an imbalanced patchwork of services, heavily skewed towards southern England, all relying to some degree on charitable donations but some receiving much more state support than others. Unsurprisingly, there are tensions and rifts.

Talks are due to take place Thursday to try to bridge a growing divide between the Association of Air Ambulances, which represents 14 of the 19 services in Britain, and the Air Ambulance Service (AAS), which operates two services, one for Warwickshire and Northamptonshire and another for Derbyshire, Leicestershire and Rutland. The AAS says it takes not a penny of state or lottery funding, and is critical of other services for doing so at a time when the NHS is under acute strain.

While this difference of approach is cause enough of ill-feeling, relations between the two sides have been soured further by the AAS's launch of the Children's Air Ambulance (CAA), a self-styled national service for the transfer of critically ill babies and children to or between hospitals. The Association of Air Ambulances questions the need for the service and accuses the AAS of jeopardising other groups' income by its aggressive fundraising activities – including the opening of CAA-branded charity shops far beyond its Midlands heartland.

Clive Dickin, the association's national director, says the AAS is sowing confusion among donors that "will ultimately almost certainly lead to a drop in fundraising income for all [air ambulance] charities".

Rather like hospices, which on average get a third of their income from the government, air ambulances have developed alongside the NHS, but are complementary to it. We are talking here primarily about "Hems", helicopter emergency medical services, which airlift casualties to hospital. However, the precise role of the individual services varies widely: London's Air Ambulance responds only to major trauma incidents, whereas other services will fly to "retrieve" people who have suffered heart attacks or broken bones and will undertake inter-hospital transfer. Most carry only a paramedic, but the London service always has a doctor too and – another point of argument – the AAS says it now does so on 80% of its callouts.

High quality

As this suggests, the AAS presents its service as being high quality. It stresses its exacting standards (claiming to have pioneered consultant-led clinical practice in the sector) and rigorous training regime. AAS also points out that, unlike most of the other charities, it has direct registration with the Care Quality Commission (CQC), the healthcare regulator.

Andy Williamson, AAS chief executive, does not hold back from criticising what he sees as unacceptable practice elsewhere. While insisting it is "nonsense" to think the AAS is aiming to take over the other charities, Williamson says: "There is a lot of money being wasted that could be better used." Joint operation of services by one organisation is more efficient and cost-effective, he argues, and brings demonstrable patient benefits.

To be sure, the AAS's very name, adopted in 2011, smacks strongly of ambition. Williamson, who has a background in the charity sector with the former Cancer Research Campaign, Marie Curie and the NSPCC, explains that a generic and simple title was needed for the umbrella group with the impending launch of the children's service. But the choice rankles with others. Graham Hodgkin, chief executive of London's Air Ambulance, says: "The AAS is clearly combative and clearly confusing in terms of the general public."

Yet even Hodgkin, a former investment banker brought in this year to grow the London service's funding base, admits to admiration of the AAS's fundraising record. Its total income shot up from £5.5m in 2011 to £9.4m last year, although its fundraising costs – £1.6m in 2011 – have been substantial and it courted the wrong kind of publicity by paying for stars of the BBC's Strictly Come Dancing show to help lead a staff team-building day. Williamson's remuneration in 2011 was more than £110,000.

Alex Toft, AAS's director of clinical service and operations, who joined from the biotech sector, says: "We are a change agent. We do push the envelope. If that makes us unpopular along the way, so be it."

The AAS's extensive fundraising – it has 26 charity shops, including two under the CAA banner in Crouch End and Muswell Hill, both in north London, and is "opening new shops all the time" – means that it pays for everything it does. From the moment it is called on by ambulance control, it says, no cost falls on the NHS. Most other charities rely on paramedics provided by the local ambulance services with which they work, or get all their drugs and equipment from them, while some simply fundraise to lease a helicopter for the NHS. Only if the charity itself provides patient care, defined as "treatment of disease, disorder or injury", is CQC registration required.

London's Air Ambulance, which in the past has had sponsorship from Express Newspapers and Virgin, had 18 personnel seconded from the NHS in 2011-12 at a value of more than £1.2m. In addition, the charity received an NHS grant of almost as much again, representing more than a third of its cash income.

Williamson, who estimates that the NHS is putting £60m a year into air ambulances, thinks they should be funded much more, perhaps entirely, by charity. "It's a hugely expensive business, but it's easier to fundraise for something like this than it is for, say, mental health or care of older people. That's where the NHS money should be going, especially at a time like this." He has harsh words, too, for air ambulance charities sitting on big cash reserves while still taking state aid. "There's £75m held in reserves by air ambulance charities around the country," he says. "We need to be pulling together to use some of this money better."

At the Air Ambulance Association, which also represents three-quarters of ambulance services and the leading helicopter leasing operators, Dickin insists it is unexceptional for a charity to be holding "£6m or £7m" in reserves to ensure its services could continue for up to 18 months in the event of a sudden loss of income, and/or to save for replacement aircraft.

's talks between the association and the AAS are likely to focus largely on the latter's new children's service. It is a costly operation – the designated helicopter needs £134,000 a month to stay operational and carries £300,000 of equipment, including a £25,000 paediatric stretcher designed for the job. It undertook its first mission in May, flying a one-day-old baby between hospitals in Scarborough and Hull in 15 minutes, when the journey by road would have taken a good hour. Yet critics say the overall operation took almost five hours, allowing for collection of a specialist NHS clinical team from Leeds and the return flight to the AAS base in Coventry, and they question its cost-effectiveness.

Lack of evidence

Dickin says there is "currently no clinical evidence" to justify the CAA service when his members already fly paediatric transfers, though the association is carrying out its own assessment of the case. But Williamson insists the AAS went ahead only after establishing there was a clear demand for its help with some of the 5,800 such transfers taking place every year.

"The doctors are the ones who wanted a nationwide specialist air transfer service for critically ill children and we responded to that need," Williamson says. "We are doing virtually one move every day now and I'm confident that demand is only going to grow. There was a great debate about whether it was needed – there still is – but we've just got on with it."